Method, device, and interface for transmitting data

ABSTRACT

A method, a device, and an interface for transmitting data between at least two subscribers, at least one first subscriber transmitting a pulse-width-modulated data signal. The at least second subscriber for its part transmits an asynchronous data signal, which is composed of binary signals, both subscribers transmitting the data, in each case, at a different, specifiable transmission rate. In this context, one of the two transmission rates, in particular that of the second subscriber, is adjusted, in particular increased, so that the pulse-width-modulated data signal of the first subscriber is simulated by a number of the binary signals of the asynchronous data signal.

FIELD OF THE INVENTION

[0001] The present invention relates to a device, a method, and aninterface for transmitting data between at least two subscribers, atleast one first subscriber transmitting a pulse-width-modulated datasignal.

BACKGROUND INFORMATION

[0002] The transmission of data in the form of a pulse-width-modulatedsignal is described in PCT Publication No. WO 98/05139. In one specificembodiment of synchronized data transmission, two different informationpulses and a synchronization pulse are generated using different pulselengths. In this manner, as a result of the three different stateswithin the context of one pulse-width modulation, both data informationas well as synchronization information can be transmitted. In thiscontext, the use of this method, cited in the related art, and the useof the corresponding interface for data transmission is represented inthe aforementioned document, in particular, as applied in a motorvehicle, for example, in the connection between a voltage regulator andthe electrical system of a motor vehicle, or as the connection betweenthe voltage regulator and the microcomputer of the digital engineelectronics as a component of the control unit.

[0003] In addition to a multiplicity of other application possibilities,such as in machine tools, i.e., in the area of producer goods, or in thearea of commodity goods, it is precisely in the automobile area that, asa result of the continued expansion of electronic systems and theircross-linking, the necessity is increasingly evident of replacingconventional wiring by bus systems and sub-bus systems.

[0004] In this context, in particular, as a central main bus system, aCAN bus, for example, is used, to which, in the automobile area, e.g.,for the closing system or an electronic window lift system, etc., asub-bus system is coupled, especially via a gateway.

[0005] Sub-bus systems of this type are robust and simple local bussystems, usually having low transmission rates, generally beingsubordinated to a main bus system such as CAN. Sub-bus systems of thistype are generally configured as master-slave systems, the subscriber,or nodes, that carry out the master function frequently possessing thegateway to the superordinate main bus system. Known sub-bus systems inhis connection are the BSS system (bit-synchronous interface) and theLIN bus system (local interconnect network). In the case of sub-bussystems such as LIN or BSS, different sub-bus protocols are generallyused. This means that the systems use the same physical layer butdifferent data bit codings. Thus in the case of the LIN bus system, astandard NRZ coding (not return to zero) is used, whereas in a BSS bus aphase modeling, specifically a pulse-width modeling, is used as thecoding.

[0006] Heretofore, sub-bus systems of this type, especially the twoaforementioned, have been so different that they cannot communicate whenmixed. For the hardware of systems of this type, this results in thefact that either a variant must be selected or the costs forimplementation sharply increase. Furthermore, as a result, theflexibility of changing from one to another bus system, or bus protocol,is sharply limited. Thus, heretofore, only special, very expensiveelectronic circuits, or components, and very expensive softwareimplementations have been capable of imaging a sub-bus protocol, forexample using pulse-width-modulated data coding, onto another sub-busprotocol, or onto another sub-bus controller, for example, usingasynchronous, binary data coding.

[0007] Thus the objective comes about to realize, using a simplearrangement, this type of mixed communication between different bus,especially sub-bus systems.

SUMMARY OF THE INVENTION

[0008] This objective is achieved by a method, a device, and aninterface for transmitting data between at least two subscribers, atleast one first subscriber transmitting a pulse-width-modulated datasignal and the at least second subscriber transmitting an asynchronousdata signal which is composed of binary signals. In this context, bothsubscribers transmit the data in each case at a different, specifiabletransmission rate. Advantageously, at least one of the two transmissionrates, in particular that of the second subscriber, is adjusted, inparticular increased, such that the pulse-width-modulated data signal ofthe first subscriber is simulated by a number of binary signals of theasynchronous data signal.

[0009] In this manner, in an advantageous way, a bit-synchronous datastream, especially in the context of the BSS bus system, can begenerated using a standard controller component, for example, a UARTcomponent (Universal Asynchronous Receiver/Transmitter). It is alsoadvantageous that, for example, an SCI protocol (Scalable CoherentInterface IEEE Standard 1596 in 1992) can be converted, so that asystem, for example, designed for the LIN bus, can be integrated into apulse-width-modulated bus system, for example, BSS, without modifyingthe hardware.

[0010] Thus, in an advantageous manner, the mixed communication ofdifferent bus systems, specifically sub-bus systems such as LIN or BSS,is possible using a simple arrangement. Advantageously, thepulse-width-modulated data signal of the first subscriber in one timesegment is simulated by a number of binary signals of the asynchronousdata signal, the time segment being stipulated and/or determined as afunction of the transmission rate of the first subscriber.

[0011] Advantageously, the number of binary signals by which thepulse-width-modulated data signal is simulated is stipulated and/ordetermined as a function of the transmission rate of the asynchronousdata signal.

[0012] Also advantageous is the fact that at least the transmission rateof the asynchronous data signal of the at least second subscriber can bevariably stipulated such that the number of binary signals per timesegment can be adjusted, it being possible to determine the time segmentfrom the transmission rate of the pulse-width-modulated data signal.

[0013] Furthermore, it is expedient that in one special embodiment thedata of the asynchronous data signal are transmitted in data groups madeof binary signals having one start binary signal, at least one stopbinary signal, and at least one data binary signal transmitted betweenthe start binary signal and the stop binary signal, as is the case, forexample, in a UART controller.

[0014] In one specific embodiment, specifically BSS, the data aretransmitted as synchronized by the pulse-width-modulated data signalsuch that at the beginning of the data transmission at least onesynchronization signal is transmitted.

[0015] With reference to the specific embodiments, this means that at adata rate that is raised repeatedly, with regard to the SCI protocol,i.e., for example the LIN bus, in comparison to the known data rates onthe BSS bus, a communication is possible on the two different bussystems. Advantageously, via specific data patterns in the data byte ofan asynchronous component, for example a UART controller, the phases inthe bit timing of the BSS protocol are simulated and are reconstructedupon reception.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 depicts a bus, specifically a sub-bus system, in which themaster function is carried out by an asynchronous network node,specifically an LIN master system, further, specifically BSS slave nodesbeing linked via the bus system.

[0017]FIG. 2 depicts a further bus, specifically a sub-bus system, inwhich the master function is carried out by a subscriber that carriesout pulse-width-modulated data transmission, specifically in a BSSmaster system. To the latter, via a bus system, an asynchronous slavesystem, specifically an LIN slave system, is connected, along withfurther nodes.

[0018]FIG. 3, by way of example, depicts the signal characteristic of apulse-width-modulated data signal.

[0019]FIG. 4 depicts the data coding of an asynchronous data signal aswell as the imaging of the pulse-width-modulated data signal by theasynchronous data signal.

[0020]FIG. 5 once again depicts the connection of thepulse-width-modulated data signal having in each case an asynchronousdata word and a blur arising therein in the context of tolerances withinthe data signals.

DETAILED DESCRIPTION

[0021] In what follows, for a pulse-width-modulated data signalaccording to the present invention, a BSS data stream as well as thecorresponding protocol are described, and for the asynchronous datasignal, an LIN data stream as well as the corresponding protocol, oraccordingly a standard UART controller, are described. These concreteexamples are used in the context of the exemplary embodiment, but theydo not limit the subject matter according to the present invention, withreference to a pulse-width-modulated protocol as well as to anasynchronous protocol.

[0022]FIG. 1 depicts a bus system 103, which, as a line system or as aline, presents the basis for the physical layer of an OSI layer model,but which is not part of the physical layer. Connected thereto at 104and 105 are slave nodes, specifically BSS slave nodes. These slave nodescan be integrated in actuators, sensors, or the like, or they can becoupled to bus system 103. Optionally, further subscribers or nodes 106,for example gateways to further sub-bus systems, can be connected. Themaster function in FIG. 1 is realized, for example, by an LIN mastersystem 100 having a line driver 101 as well as a controller and UARTcomponent 102. In this context, controller 102 can also function as aninterface, in accordance with the present invention, of the BSS systemto an LIN bus system.

[0023] A sub-bus system of the type depicted in FIG. 1 predominantlyacts to cross-link actuators and sensors in one small area, for example,within a car door. Systems of this type are frequently designed asmaster-slave systems, the sub-bus master usually also having availableto it a further interface to the main system bus, for example, a CAN ora TTP bus, for connecting to the global network. On the other hand, thesub-bus master can also be a part of a control unit, in particular forcontrolling operational sequences in a motor vehicle.

[0024] To reduce the customary networking costs, the aforementionedsub-bus systems are used in place of customary cabling or wiring. Line103 functions as the basis for the bit-transmission layer, the so-calledphysical layer corresponding to the OSI layer model, but it itself isnot a component of this layer. The bit transmission layer is theelectrical or functional interface to the physical transmission medium,in this case to the line.

[0025] Instead of an LIN master system, as in FIG. 1, a BSS mastersystem can also be present. In this context, BSS master 200, forexample, maintains an interface or gateway to the main bus system, suchas CAN, and at the same time a connection to bus system 103. Connectedto the latter via 201 is an LIN slave system. The latter for its partcontains a line driver 202 as well as a controller and UART component203. Further sub-bus systems and sensors or actuators can also beconnected to the LIN slave system as well as to the LIN master systemvia interfaces, for example, of the controller or of UART, here, too, atleast parts, such as the controller or UART of the LIN slave system,being able to be used as the interface according to the presentinvention for the mixed communication of an LIN system with a BSSsystem.

[0026] At 204, further subscribers, for example as BSS nodes or LINslave systems, are connected to bus system 103. Here, too, slavesystems, or nodes, as subscribers can be integrated in the specificelements to be connected, especially actuators and sensors, or they canbe connected to the bus system in other ways. Optionally, furthersubscribers 205 can be connected to the bus system; similarly furthersub-bus systems can be connected by a gateway.

[0027] The information to be transmitted or the data to be transmittedof the BSS protocol, as was already stated, are represented inpulse-width-modulated form. A depiction of this type is disclosed inFIG. 3. There, by way of example, in a voltage-time diagram, specificvoltage level U1, or U2, is depicted over time t. In this context,low-level U1, or zero (“0”) level, is, for example, ground GND, andhigh-level, or one (“1”) signal U2, corresponds, for example, to asupply voltage, in particular to battery voltage U_(bat).

[0028] Represented by 300 is the signal characteristic of a first state,of the synchronization information, or of synchronization signal sync.In this context, the synchronous time interval for low-level T_(sync)is, for example, ⅛ of total cycle duration T_(per). This total cycleduration for the pulse-width-modulated signal can be set by stipulatingthe transmission rate.

[0029] Indicated characteristic 301 of the data signal corresponds to alow signal information message having a zero or low signal time intervalT_(low). In this context, T_(low) is, for example, ⅜ of the total cycleduration. Using this pulse length, it is possible to represent, forexample, the zero or low information message.

[0030] The third state to be depicted is the high or one-signalinformation message, which is indicated by signal characteristic 302. Inthis context, T_(high) or the high signal time interval is, for example,{fraction (6/8)} of total cycle duration T_(per). Every othersubdivision of the individual pulse width for the three states can alsobe used. Thus, here, by way of example, three states can be representedby the signal characteristics 300, 301, and 302, which are used torealize a synchronization information message, a low-signal informationmessage, or a high-signal information message. In this way, any data canbe transmitted in synchronized form.

[0031] Pulse-width-modulated data signals of this type are used, forexample, in the context of the BSS protocol. In this context, periodicsync pulse sync comes from the master system. All slaves or slavesystems, in this context, synchronize to the falling or low edge.

[0032] In FIG. 4, the pulse-width-modulated depiction described in FIG.3 is once again represented. This means, for example, in a BSS protocol,the data information message is coded into the pulse width of oneperiodic signal. To simulate this information message using, forexample, an NRZ-coded data stream having binary signals, thetransmission rate in the NRZ data stream is now increased (the same, ofcourse, applies also to an RZ data stream). I.e., to represent the BSSbit timing, a plurality of data bits is used in the NRZ data stream.

[0033] In 400, an NRZ-coded data signal characteristic of this type isdepicted so as to be preferably asynchronous. In this example, totalcycle duration T_(per) from FIG. 3 is simulated using 8 (data) binarysignals, or data bits, as well as one start binary signal, or start bitS1, and one-stop bit S2. In this context, every other data bit number,with or without start or stop bit, can be used as the number of binarysignals, as a function of the transmission rate. Thus, for example, asimulation is possible that also uses 4 data bits in place of 8 databits or 10 bits. If the transmission rate of the LIN system, or of theUART controller, is selected so that, for example, one byte plus startand stop bit includes two cycle time durations T_(per), i.e., that twocycle time durations can be simulated using a total of 10 bits, then twoBSS-coded information messages, beginning at start bit S1 andterminating at stop bit S2, can be simulated. In this context, a highlevel of the simulating system is depicted at U3, and a low level of thesame at U4. These levels can be selected as desired, or besystem-immanent, and they can also correspond to levels U1 or U2,respectively.

[0034] Commencing with start bit S1, the following byte, i.e., the databits 0 through 7, can be set as binary signals as desired, to simulatethe data signal in accordance with signal characteristics 300, 301, or302. If, for example, the data signal characteristic according to 301 issimulated, then, as is depicted in signal characteristic 401, the startbit and the first four data bits are set at the low level, i.e., atlevel U4. Thus signal characteristic 301 can be simulated in the contextof specific tolerances in the bit timing. This is also possible withrespect to signal characteristic 302 using signal characteristic 402, inwhich, in addition to the start bit, for example, the first 6 bits aretransmitted at a low level. Similarly, the synchronization signal isindicated, e.g., at S1, at an equally low level.

[0035] As can be seen here, as a result of the choice of thetransmission rate of the pulse-width-modulated signal, i.e., of cycleduration T_(per) of the latter, and as a result of the choice of thetransmission rate of the simulating data signal, the resolution of thebit simulation can be set as desired.

[0036] Since, for example, a BSS node in accordance with the BSSspecification, can have a transmitting tolerance of +/−3% of the typicalvalue, the pulse-width-modulated signal can generally be simulated onlyapproximately, in particular using the preestablished subdivision of thestart, data, and stop bits. In addition, certain imprecisions areconceivable if the transmission rates of the two data streams cannot beconverted one to the other in precise whole numbers.

[0037] Since, in addition, both the transmission as well as thereceiving tolerances in pulse-width-modulated data signals, especiallyrelated to the BSS specification, permit temporal deviations of the edgechange, it is important to distinguish whether, on the one hand, thedata transmitted by the asynchronous interface, in particular the UART,can be read by a BSS node, or whether, on the other hand, thepulse-width-modulated signals of a BSS node can be correctly detectedand interpreted at a microcontroller, UART.

[0038]FIG. 5 depicts an assignment of this type of pulse-width-modulatedsignal, in each case, to an asynchronous data word. In the table, startand stop bits are ignored because they can be detected clearly. Theambiguity of the data bits is caused by the different possible timepoints of the edge change in the context of the tolerance, as well as bythe type of bit detection of the UART using oversampling, and thisambiguity is designated by “X.”

[0039] If, as is the case here, only {fraction (1/10)} of cycle durationT_(per) is used as a subdivision for representing thepulse-width-modulated signals, nevertheless an unambiguous distinctioncan take place. Thus synchronization signal sync and low signal low canclearly be distinguished using data bit 1. Similarly, the low and highsignal high, in this example, can be clearly distinguished using databit 4. This means that even bad asynchronous controllers, in particularUARTs, which do not perform, for example, any rejections of the scanningvalues lying in the edge range of the signals, can be used even withoutforming an average value of the non-rejected signals.

[0040] Conversely, for the reception of a synchronous pulse at the UART,the possibility results of using in binary representation 01111111 (databits 0-7) or 11111111 in hexadecimal representation FF and FE. A 0 orlow information message can be represented using FC, F8, and F0(hexadecimal). The 1 or high information message, with reference to thisexample, can be depicted using E0, C0, 80 and 00 (hexadecimal). Thus,despite different subdivisions of BSS pulses and UART bits, the pulsescan be both received as well as transmitted by the asynchronousinterface.

[0041] Using the present invention, there is therefore in principle thepossibility of having sub-bus systems, or sub-bus components havingpulse-width-modulated data signals and sub-bus systems and sub-buscomponents having asynchronous, especially NRZ-coded data signals,communicate in mixed form, this being possible, especially in BSS andLIN, on the same hardware. In this way, sub-bus protocols of this type,or the corresponding data signals, can be used as required in theidentical hardware configuration or can be exchanged one for the other.

[0042] In this context, at least one of the two transmission rates, inparticular data of the asynchronous data stream, i.e., of the UART, orLIN system, is adjusted, in particular increased, so that thepulse-width-modulated signal can be simulated by a number of binarysignals. For this purpose, a reduction (or increase) of the transmissionrate of the pulse-width-modulated signal is just as conceivable as anincrease (or reduction) of the transmission rate of the asynchronous, inparticular NRZ data stream.

What is claimed is:
 1. A method for transmitting data between at leasttwo subscribers, comprising the steps of: causing at least a first oneof the at least two subscribers to transmit a pulse-width-modulated datasignal at a first specifiable transmission rate; causing at least asecond one of the at least two subscribers to transmit at a secondspecifiable transmission rate an asynchronous data signal that includesbinary signals, wherein: the first specifiable transmission rate and thesecond specifiable transmission rate are different from each other; andadjusting one of the first specifiable transmission rate and the secondspecifiable transmission rate such that the pulse-width-modulated datasignal is simulated by a number of the binary signals of theasynchronous data signal.
 2. The method according to claim 1, wherein:the step of adjusting includes increasing the second specifiabletransmission rate.
 3. The method according to claim 1, furthercomprising the steps of: simulating the pulse-width-modulated datasignal in one time segment by the number of the binary signals of theasynchronous data signal; and at least one of stipulating anddetermining the asynchronous data signal as a function of the firstspecifiable transmission rate.
 4. The method according to claim 1,further comprising the step of: at least one of stipulating anddetermining the number of the binary signals that simulate thepulse-width-modulated data signal as a function of the secondspecifiable transmission rate.
 5. The method according to claim 1,further comprising the step of: variably stipulating at least the secondspecifiable transmission rate such that, as a result, the number of thebinary signals per time segment, which can be determined from the firstspecifiable transmission rate, can be set.
 6. The method according toclaim 1, further comprising the step of: transmitting data of theasynchronous data signal in data groups made of the binary signalsincluding a start binary signal, at least one stop binary signal, and atleast one data binary signal transmitted between the start binary signaland the at least one stop binary signal.
 7. The method according toclaim 1, wherein: data are transmitted in synchronized form by thepulse-width-modulated data signal such that at a beginning of a datatransmission at least one synchronization signal is transmitted.
 8. Adevice for transmitting data, comprising: at least a first subscribertransmitting a pulse-width-modulated signal at a first specifiabletransmission rate; at least a second subscriber transmitting anasynchronous data signal including binary signals at a secondspecifiable transmission rate; a connection for performing a datatransmission; and an arrangement for adjusting at least one of the firstspecifiable transmission rate and the second specifiable transmissionrate in order to simulate the pulse-width-modulated data signal by anumber of the binary signals of the asynchronous data signal.
 9. Thedevice according to claim 8, wherein: the arrangement for adjustingincreases the second specifiable transmission rate.
 10. An interface fortransmitting data between at least a first subscriber and at least asecond subscriber, the at least first subscriber transmitting apulse-width-modulated data signal at a first specifiable transmissionrate, and the at least second subscriber transmitting at a secondspecifiable transmission rate an asynchronous data signal that includesbinary signals, the interface comprising: an arrangement for adjustingone of the first specifiable transmission rate and the secondspecifiable transmission rate in order to simulate thepulse-width-modulated data signal by a number of the binary signals ofthe asynchronous data signal.
 11. The interface according to claim 10,wherein: the arrangement for adjusting increases the second specifiabletransmission rate.